Metabarcoding and microscopy characterization of planktonic protist assemblages from frontal areas of the Argentine sea

ALMANDOZ G. O.; SPRONG, P.; FABRO, E; BARRERA, F.; MASCIONI, M.; ANTONI J.; FERRARIO, M. E.; METFIES, KATJA

virtual

Jornada; XXXVIII Jornadas Argentinas de Botánica; 2021

Sociedad Argentina de Botánica

The Argentine Sea is worldwide recognized as a highly productive area, with large phytoplankton blooms occurring in spring-summer. Despite the well-known importance of frontal areas for biomass accumulation, phytoplankton diversity remain al-most unexplored. Here we studied protist compo-sition during January 2016 by 18S metabarcoding and microscopy in three tidal fronts located from ≈43 to 55° S. Protist composition varied along lati-tudinal and inshore-offshore gradients. An assem-blage largely dominated by an OTU assigned to the prasinophyte species Pycnococcus provasolii was observed at Valdés front, where microscopy revealed a bloom of 11.6×106 cells L-1. A second as-semblage mainly represented by OTUs assigned to picoplanktonic prasinophytes (Clade VIII) and Picochlorum sp. (Trebouxiophyceae), the diatom Minidiscus trioculatus and the dinoflagellate Gy-rodinium fusiforme was observed at Blanco Cape front, with increasing dinoflagellate abundance to-wards stratified waters. Diatoms notably increased at de los Estados Island front, mainly represented by an OTU assigned to Chaetoceros contortus, coinciding with an abundance of 2.0×105 cells L-1 of Chaetoceros spp. Moreover, the presence of cold-water species, such as Phaeocystis antarctica, Chaetoceros atlanticus, and Fragilariopsis kergue-lensis, was detected off-shore. Our results suggest a strong influence of water masses and local hydro-graphic conditions on protist distribution.